Universal joints are commonly used in automotive, agricultural, aeronautical, and industrial applications to couple two rotary shafts that have an angular misalignment along the axis of rotation of each shaft. One type of universal joint is aptly referred to as a constant velocity (CV) universal joint. A CV universal joint operates to minimize the rotational variations between drive and driven shafts at an angle to one another. A typical CV universal joint comprises a housing, a pair of yokes, a pair of cross members with each cross member pivotally connecting one of the yokes to one of the ends of the housing, and a centering apparatus orbitally mounted in the housing between the yokes. A drive shaft is connected to one of the yokes and the driven shaft is connected to the other yoke. The centering apparatus operates to equalize the angles between the drive shaft and housing, and the driven shaft and housing, thus providing a near constant velocity ratio between the drive and the driven shafts.
Repeated metal-to-metal sliding contact within the centering apparatus has presented a challenge in prior universal joints. Lubrication has been the most prevalent solution, however, it is difficult to ensure the lubrication is both applied in the proper location and remains in that location during operation of the universal joint. Under general operation, centrifugal forces act on the lubricant and tend to displace the lubricant radially outward from the center of rotation. See, for example, U.S. Pat. No. 4,781,662 issued to Mayhew et al., which is hereby incorporated by reference in its entirety.